Cyclone separator

ABSTRACT

This invention is about a cyclone separator, and may be applied to the cyclone separators disclosed and claimed in UK Pat. Nos. 1583742, 1583730 or 2102311, or those described in UK Patent Application 8419771 or 8511149 or 8515264. Thus, application 8419771 describes a cyclone separator which has an inlet portion having generally the form of a volume of revolution with a single tangential inlet (preferably with an involute feed channel, for introducing feed to be separated into the cyclone separator and, adjacent to the inlet portion and substantially coaxial therewith, a generally axially symmetrical separation portion converging uninterruptedly into a downstream portion. The inlet portion has an axial overflow outlet opposite the separation portion (i.e. in its end wall). The involute feed channell may be fed from a duct directed tangentially into the inlet portion, the (outer) wall of the channel converging to the principal diameter of the inlet portion, preferably by substantially equal radial decrements per unit angle around the axis, preferably attaining the principal diameter after 360° around the axis.

Application 8511149 describes a cyclone separator which has an inletportion having generally the form of a volume of revolution with asingle inlet (preferably tangential, and preferably with an inwardsspiralling feed channel such as an involute entry) for introducing feedto be separated into the cyclone separator and, adjacent to the inletportion and substantially coaxial therewith, a generally axiallysymmetrical separation portion converging (preferably uninterruptedly)into a downstream portion. The inlet portion has an axial overflowoutlet opposite the separation portion (i.e. in its end wall). In thecyclone separator, the following relationships (i)-(v) apply: where d₁is the diameter of the cyclone in the inlet portion where flow enters(but neglecting any feed channel), d_(i) is twice the radius at whichflow enters the cyclone (i.e. twice the minimum distance of thetangential component of inlet centreline from the axis), A_(i) is thecross-sectional area of the inlet at entry to the cyclone in a planeparallel to the axis of the cyclone and perpendicular to the componentof the inlet centreline not parallel to the cyclone axis, d₂ is thediameter of the cyclone where the inlet portion joins the separationportion the point of junction being defined as being at the axialposition z₂ (measured away from the inlet plane) where the conditionfirst applies that: ##EQU1## for all z>z₂ where d is the cyclonediameter at z, d₃ is the cyclone diameter where the separation portionjoins the downstream section and is defined as the diameter at z₃ whered/d₃ ≧0.98 for all z≧z₃, d_(o) is the minimum internal diameter of theaxial overflow outlet, then: ##EQU2##

    20'<α<2°                                      (ii)

where α is the half angle of convergence of the separation portion, i.e.##EQU3##

    d.sub.o /d.sub.2 <0.2                                      (iii)

    0.9 d.sub.1 >d.sub.2                                       (iv)

    0.9 d.sub.2 >d.sub.3.                                      (v)

The cyclone separator of application 8515264 has an inlet portion havinggenerally the form of a volume of revolution with n inlets where n>1(each inlet preferably tangential, and preferably with an inwardsspiralling feed channel such as an involute entry) for introducing feedto be separated into the cyclone separator and, adjacent to the inletportion and substantially coaxial therewith, a generally axiallysymmetrical separation portion converging (preferably uninterruptedly)into a downstream portion. Where the feed channels do not spiralinwards, or where they are not axially staggered, at least part of thegenerator of the inlet portion and/or of the separation portion iscurved. The inlet portion has an axial overflow outlet opposite theseparation portion (i.e. in its end surface) In the cyclone separator,the following relationships (i)-(v) apply: where d₁ is the diameter ofthe cyclone inlet portion. where flow enters (but neglecting any feedchannel), d_(ix) is twice the radius at which flow enters the cyclonethrough the x-th inlet (i.e. twice the minimum distance of thetangential component of inlet centreline from the axis), and ##EQU4##A_(ix) is the total cross-sectional area of the x-th inlet measured atentry to the cyclone in a plane parallel to the axis of the cyclone andperpendicular to the component of the inlet centreline not parallel tothe cyclone axis, ##EQU5## d_(i) is the diameter of the cyclone wherethe inlet portion joins the separation portion the point of junctionbeing defined as being at the axial position z₂ (measured away from theinlet plane where z=0) where the condition first applies that: ##EQU6##for all z>z₂ where d is the cyclone diameter at z, z =0 being theposition of the axial centroid of the inlets, d₃ is the cyclone diameterwhere the separation portion joins the downstream section and is definedas the diameter at z₃ where d/d₃ >0.98 for all z>z₃, d_(o) is theminimum internal diameter of the axial overflow outlet, then: ##EQU7##

    20'<α<2°                                      (ii)

where α is the half angle of convergence of the separation portion, i.e.##EQU8##

    d.sub.o /d.sub.2 <0.2                                      (iii)

    0.9 d.sub.1 >d.sub.2                                       (iv)

    0.9 d.sub.2 >d.sub.3.                                      (v)

In those cyclone separators in use, the major volumetric component isthe continuous phase, with up to a few percent of less dense phase andwith perhaps up to about 1 part per thousand by volume finely dividedsolids or other more dense phase. Priority is usually given to a highlypurified continuous phase over minimising the volume of the outletstream containing the less dense phase. Both features, while typical ofuse of the cyclone separators set forth above, are most unlike the vastmajority of cyclone separator technology.

The drawing shows the best mode of the invention.

According to one aspect of the present invention there is provided acyclone separator comprising a separating chamber; at least one inletfor introducing feed to be separated into the cyclone separator and atleast two outlets for discharging material from the separating chamberat least one slot disposed in the wall of said separating chamberdownstream of the or each said inlet said slot leading to orcommunicating with an exit from said separating chamber.

Preferably the or each slot is generally circumferential and extends atleast partially around the wall of said separating chamber. In one formtwo slots are dhsposed on the same circumferential line in spaced apartrelation. In another form the slot extends continuously around the wallof the separating chamber.

There may be further provided a valve to control the discharge ofmaterial from said exit so that a selected proportion of the materialflowing through the chamber leaves through that exit.

Preferably up to 15% by volume of the material leaves through said exit.

Preferably the slot extends radially outwardly with substantially planaredges and free from radially inwardly extending protusions into the bodyof the cyclone separator.

In one form the separating chamber comprises at least a primary portionhaving generally the form of a volume of revolution and having a firstend and a second end, the diameter at said second end being less thanthe diameter at said first end said single inlet having at least atangential component and being disposed at or adjacent said first endfor introducing feed to be separated into the cyclone separator in whichcyclone separator the following relationship applies: where d_(i) is thediameter of the cyclone in the primary portion where flow enters (butneglecting any feed channel), d_(i) is twice the radius at which flowenters the cyclone (i.e. twice the minimum distance of the tangentialcomponent of the inlet centre line from the axis), A_(i) is thecross-sectional area of the inlet at entry to the cyclone in a planparallel to the axis of the cyclone and perpendicular to the componentof the inlet centre line not parallel to the cyclone axis, d₂ is thediameter of the primary portion at said second end and is measured at apoint z₂ where the condition first applies that: ##EQU9## for all zgreater than z₂ is the distance along the cyclone separator axisdownstream of the plane containing the inlet and d is the diameter ofthe cyclone at z then: ##EQU10## is from 3 to 12.

In another form the separating chamber comprises at least a primaryportion having generally the form of a volume of revolution and having afirst end and a second end, the diameter at said second end being lessthan at said first end, a plurality of n inlets, where n>1, each saidinlet having at least a tangential component at or adjacent said firstend for introducing feed to be separated into the cyclone separator andthe separator further including at least two outlets, in which cycloneseparator the following relationship applies:

where d is the diameter of the said primary portion where flow enters(but neglecting any feed channel), d_(ix) is twice the radius at whichflow enters the cyclone through the x^(th) inlet (i.e. twice the minimumdistance of the tangential component of the inlet centre line from theaxes) and ##EQU11##

where A_(ix) is the total cross sectional area of the x^(th) inlet atentry to the cyclone separator in a plane parallel to the axis of thecyclone separator and perpendicular to the component of the inlet centreline not parallel to the cyclone axis, and where ##EQU12## and where d₁is the diameter of the primary portion at said second end and ismeasured at a point z₂ where the condition first applies that ##EQU13##for all z>z₂ where z is the distance along the cyclone separator axisdownstream of the plane containing the inlet and d is the diameter ofthe cyclone at z, and further z=0 being the axial position of theweighted areas of the inlets such that the injection of angular momentuminto the cyclone separator is equally distributed axially about saidaxial position where z=0 and being defined by ##EQU14## where z_(x) isthe axial position of the x^(th) inlet and further ##EQU15## is from 3to 12.

According to another aspect of the invention there is provided a methodof separating a material containing (i) a volumetrically predominantcontinuous phase, (ii) a dispersed phase less dense than phase (i), and(iii) a dispersed phase more dense than phase (i), comprising applyingthe material to the inlet(s), phase (ii) predominantly reporting to anaxially disposed one of said outlets and phase (iii) predominantlyreporting to the exit through the slot.

Thus in the present invention, there is provided; a separating chamber;at least one inlet for introducing feed to be separated into the cycloneseparator and at least two outlets for discharging material from theseparating chamber; at least one generally circumferential slot disposedin the wall of said separating chamber downstream of the or each saidinlet said slot leading to or communicating with an exit from saidseparating chamber. Preferably a valve is provided to control the exit,so that a desired proportion (such as up to 15% by volume) of thematerial flowing through the cyclone leaves through that exit. The slotis preferably not wider (measured axially) than 10% of d₂. Preferablythe slot extends radially outwardly, with substantially planar edges,and free from radially inwards protrusions into the body of the cycloneseparator.

Preferably higher pressure is applied at the inlets than exists, at theoutlets and further it is preferable that the axial outlet is anoverflow outlet.

Preferably, the dispersed phase (ii) is under 5% by volume (morepreferably under 1%) of the material, and may for example be hydrophobicsuch as oil.

For example the phase (i) is aqueous.

For example the phase (iii) is solids, preferably not exceeding 1 partper thousand by volume of the material and may be example be sand,quartz or clay. Preferably its kinetic energy on leaving the cycloneseparator is recovered.

The invention will now be described by way of example, with reference tothe accompanying drawing, which shows, schematically, a cycloneseparator according to the invention The drawing is not to scale.

Except as explained hereafter, the illustrated cyclone separator isidentical to that disclosed and claimed in UK Pat. No. 2102311, to whichthe reader is referred. Identical reference numbers have been used asfar as possible. Where the flow-smoothing taper T₂ of the separationportion 2 merges at its downstream end with the cylindrical thirdportion 3, a circumferential slot 20 is cut, leading to an annulargallery 21 which has occasional generally radial drains 22 controlled byvalves 23. The slot width (measured axially) is 3 mm, i.e. about 8% ofthe diameter d₂ (38 mm) of the separation portion 2. d₃ is 19 mm.

In treating oily water, the oil removal efficiency remained satisfactoryover a large range of split ratios at small volumetric flow ratesthrough the slot 20, i.e. up to about 15% of the flow entering thecyclone separator. When the valves 23 were fully closed, the cycloneseparator operated as if the slot 20 were absent.

The slot itself could be located anywhere along the taper T₂ where theflow was generally convergent. In a curved-wall cyclone, this would alsoapply, that is, the slot 20 could be located at any location where theflow structure was characteristic of a convergence towards thedownstream outlet.

Slot widths grossly exceeding 10% of d₂ or having radially inwardlyprotruding lips, guides or other discontinuities were found to upset theflow structure in the cyclone separator.

The effect of the slot 20, when the valves 23 are appropriately open, isto form a third exit from the cyclone separator. This is especiallysuitable where it is desired to treat a continuous liquid phase (e.g.water) containing two low-concentration dispersed phases, one denser andone less dense than the continuous phase, e.g. solids and oil The solidsmay in practice comprise sand (e.g. quartz) or clay or chalk, up toabout 1 part per thousand by volume. It is this denser phase which,centrifugally thrown radially outwardly towards the wall of the cycloneseparator, is extracted through the slot 20. The particle size of suchsolids, in two examples 20 microns and 100 microns; these simply moveinto the slot. Some particles may be carried past the slot by the flow,but this is acceptable since, for most applications, removal of saythree-quarters of the solids is sufficient.

Within the scope of this invention, the slot 20 may be applied to othercyclone separators than that in the drawing. Thus, for example, the slot20 could be applied to the cyclone separator disclosed and claimed in UKPat. No. 1583742, making it possible to treat materials containinghigher proportions of less dense phase, such as up to 5%.

More than one slot 20 may be provided at different axial positions(z>z₂).

The slot(s) thus permit a three-way separation of material at similarenergy cost as conventional two-way separation in a cyclone separator.The pressure drop in the slotted cyclone separator is similar to that inan unslotted one, and the need for extra energy-consuming sand-removalcyclones, as used conventionally, is obviated. Moreover, the kineticenergy may (at least to some extent) be recovered from the exit, byusing a suitable form of spiral or tangential connection instead ofexactly radial drains 22 from the slot 20; alternatively a diffusingaction in the slot 20 itself may be exploited to recover this energy.

We claim:
 1. A cyclone separator comprising a separating chamber;atleast one inlet for introducing feed to be separated into the cycloneseparator and at least two outlets for discharging material from theseparating chamber; means for enabling a denser phase to exit thecyclone separator other than through said outlets, and for otherwisesubstantially precluding disturbance of the flow of material beingdischarged from the separating chamber, said means including at leastone slot disposed in the wall of said separating chamber downstream ofthe or each said inlet, said slot leading to or communicating with anexit from said separating chamber.
 2. A cyclone separator according toclaim 1 wherein the or each said slot is generally circumferential andextends at least partically around the wall of said separating chamber.3. A cyclone separator according to claim 2 wherein two said slots aredisposed on the same circumferential line in spaced apart relation.
 4. Acyclone separator according to claim 2 wherein said slot extendscontinuously around the wall of said separating chamber.
 5. A cycloneseparator according to claim 2 wherein up to 15% by volume of thematerial leaves through said exit.
 6. A cyclone separator according toclaim 1 further including a valve to control the discharge of materialfrom said exit so that a selected proportion of the material flowingthrough the chamber leaves through that exit.
 7. A cyclone separatoraccording to claim 1 wherein said slot extends radially outwardly withsubstantially planar edges and free from radially inwardly extendingprotusions into the body of the cyclone separator.
 8. A cycloneseparator according to claim 1 wherein said separating chamber comprisesat least a primary portion having generally the form of a volume ofrevolution and having a first end and a second end, the diameter at saidsecond end being less than the diameter at said first end said singleinlet having at least a tangential component and being disposed at oradjacent said first end for introducing feed to be separated into thecyclone separator in which cyclone separator the following relationshipapplies: where d_(i) is the diameter of the cyclone in the primaryportion where flow enters (but neglecting any feed channel), d_(i) istwice the radius at which flow enters the cyclone (i.e. twice theminimum distance of the tangential component of the inlet centre linefrom the axis), A_(i) is the cross-sectional area of the inlet at entryto the cyclone in a plan parallel to the axis of the cyclone andperpendicular to the component of the inlet centre line not parallel tothe cyclone axis d₂ is the diameter of the primary portion at saidsecond end and is measured at a point z₂ where the condition firstapplies that: ##EQU16## for all z greater than z₂ where z is thedistance along the cyclone separator axis downstream of the planecontaining the inlet and d is the diameter of the cyclone at z then:##EQU17## is from 3 to
 12. 9. A cyclone separator according to claim 1wherein said separating chamber comprises at least a primary portionhaving generally the form of a volume of revolution and having a firstend and a second end the diameter at said second end being less than atsaid first end, a plurality of n inlets, where n>1 each said inlethaving at least a tangential component at or adjacent said first end forintroducing feed to be separated into the cyclone separator and theseparator further including at least two outlets, in which cycloneseparator the following relationship applies:where d₁ is the diameter ofthe said primary portion where flow enters (but neglecting any feedchannel), d_(ix) is twice the radius at which flow enters the cyclonethrough the x^(th) inlet (i.e. twice the minimum distance of thetangential component of the inlet center line from the axes) and##EQU18## where A_(ix) is the total cross sectional area of the x^(th)inlet at entry to the cyclone separator in a plane parallel to the axisof the cyclone separator and perpendicular to the component of the inletcentre line not parallel to the cyclone axis, and where ##EQU19## andwhere d₂ is the diameter of the primary portion at said second end andis measured at a point z₂ where the condition first applies that##EQU20## for all z>z₂ where z is the distance along the cycloneseparator axis downstream of the plane containing the inlet and d is thediameter of the cyclone at z, and further z=o being the axial positionof the weighted areas of the inlets such that the injection of angularmomentum into the cyclone separator is equally distributed axially aboutsaid axial position where z=0 and being defined by where z_(x) is theaxial position of the x^(th) inlet, and further ##EQU21## is from 3 to12.